Civilian and military sea vessels use active and passive sonar systems for numerous applications including geological studies, marine life exploration, and military operations such as anti-submarine warfare (ASW). These systems are used to detect the presence of submerged objects by either transmitting a sound wave and detecting its reflection as it propagates through the water (active sonar) or by listening for sound waves generated by these objects (passive sonar).
The relative usefulness of active versus passive sonar systems is a function of various factors. For example, active sonar is desirable for applications that require an estimated bearing and range of a potential target. This is normally accomplished by the transmission of a sound wave (a “ping”). While providing range and bearing information of a target however, this transmission also increases the likelihood of detection by other vessels.
The use of passive sonar systems may be advantageous over active systems for stealth operations, such as ASW, as a host vessel's location is not reveled by the use of these systems. A drawback of passive sonar, however, is its susceptibility to interference, particularly noise emitted from the host vessel. For example, noise from the vessel's propulsion system may negatively impact the operation of a passive system. This is especially true in the case of hull-mounted arrays, where hull-born vibrations and other noises are transferred directly to the sonar transducers. In order to locate the array further from the vessel's noise-producing components, and thus reduce interference, sonar arrays are often towed behind vessels.
These towed arrays generally comprise hydrophone arrangements that are deployed and recovered through openings in the hull of a vessel, or over the gunwale of a ship. A winch and/or boom arrangement is often utilized to recover the array. Such handling equipment occupies a large amount of deck space in addition to presenting a large target cross-section to enemy radar. Thus, these arrangements limit covert deployment and recovery. Deployment and recovery is also time consuming and difficult, particularly in high seas. Active sonar devices may also take the form of towbodies configured to be deployed and recovered by a host vessel. Conventional launch and retrieval methods include reeling in a tow-cable attached to the towbody, and hoisting the towbody into a cradle or onto a ramp arranged on the vessel.
These methods for launch and retrieval create difficulties for vessels deploying both active and passive systems. Previous solutions include increasing the size of the host vessel to accommodate independent systems for deploying and recovering active and passive sonar equipment. Other prior art systems utilize a towed line array (TLA) detachably connected to the towbody. In these systems, the TLA is disconnected from the towbody and stored after the towbody has been recovered. This arrangement requires the host vessel to be manned, and thus, is unsuited for applications in remotely operated vessels, such as unmanned surface vehicles (USVs). This is particularly detrimental as the probability of detection is increased with the use of an active sonar system, and thus, it would be advantageous to be able to implement these systems into relatively low cost platforms, including USVs.
Improved systems are desired.